Method of necking and tapering cartridge cases



June 8 1943 J. P. cATLlN ETAL D 2,442,841

` METHOD OF NECKING AND TAPERING CARTRIDGE GASES Filed Nov. 10, 1944 IN VEN TORS.

JOHN R C'ATL/N.

) GEORGE R. ECKSTEN. M/LTUN B. VRDAHL.

Patented June 8, 1948 METHOD OF NECKING AND TAPERING CARTRIDGE CASES John P. Catlin, Fairfield, and George R. Eckstein, Bridgeport, Conn., and Milton B. Vordahl, Richland, Wash., assignors to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application November 10, 1944, Serial No. 562,886

4 Claims. 1

The present invention relates, in general, to metal working and more especially to an im proved method of making tubular metallic articles such as .50 caliber cartridge cases.

As an outgrowth of the scarcity of brass for the manufa-cture of cartridge cases, extensive work has been done to .develop a satisfactory steel cartridge case. The use of steel has presented many problems not heretofore encountered in the manufacture of brass cases due primarily to the metallurgical characteristics of steel. It has been definitely established that a steel blank equal in diameter and thickness to a brass blank and subjected to cupping, drawing, annealing and tapering operations on 'the identical machines used in the manufacture of satisfactory brass cases behaves quite differently and regularly forms a case which is unsatisfactory both from the standpoint of ballistics and manufacture.

The manufacture of steel cartridge cases in quantity production lots and of a quality to meet Government specifications and to perform satisfactorily under the most severe 'tests has necessitated the development of new equipment and methods of manufacture.

The present invention relates particularly to an improved method of tapering and necking .50 caliber `steel cartridge cases; however, it has been found that the method developed as hereinafter described is applicable and beneficial in the m-anufacture of cartridge cases of other materials such as brass and aluminum; and of other than standard specifications, cases of the latter type being termed cases of heavy geometry.

An object of the invention is the provision of an improved method of -shaping metal tubular articles. A further object is to provide an improved method of tapering and necking steel cartridge cases.

Other objects, features and advantages of the invention will be described hereinafter in detail.

In the drawing:

`Fig. l is a graph showing the body anneal and taper hardness pattern with conventional tapering.

Fig. 2 is a graph showing an unusually short zone of anneal and a taper hardness pattern with preworked tapering.

Fig. 3 `shows a die stack for preworked tapering.

Fig. 4 shows schematically the four stages in tapering and necking a cartridge case in accordance with the method of this invention.

Fig. 4A is a s-chematic view showing 'the superposition of station 2 and station 4 of Fig. 4.

Briefly, cartridge cases are made by punching out a disk from a strip of metal and pres-sing th'e disk into the form of a cup. A preferred method and means of forming a cup from a steel blank for the manufacture of .50 caliber steel cases is described in detail in a copending application Serial No. 557,351, led October 5, 1944, now Patent No. 2,415,940, Yissued February 18, 1947.

The cup is pressed or drawn through a plurality of dies until it becomes an elongated tube closed at one end. The closed end of the tube is :bumped up to form the head of the case and suitable tapering and necking dies cold work the body of the case into its final shape. Metal becomes hardened when cold worked; moreover, to achieve the necessary hardness in the head and body of a steel case, the case, as drawn, that is to say after final draw, may be heated above the upper critical temperature and brine quenched. It has been the practice in making brass cartridge cases to anneal the case immediately preceding the tapering and necking operations. The purpose of such body anneal is two fold, first to facilitate the metal displacement necessary to tapering and necking, and second Ito prepare for the metallurgical properties required in different parts of the finished case. The head must be relatively hard for adequate strength, the body must approach the hardness of the head to secure the spring back which enables extraction and yet have suiiicient elasticity for obturation, that is to say the ability to eX- pand and form a gas seal between the outside of the case and the wall of the chamber. The

- shoulder must be hard enough to give adequate longitudinal support against the impact of the firing pin, but neck and mouth must be soft enough to enable stretching to receive the bullet, crimping into the bullet, and expanding to release the bullet, all without rupture. And, finally, the body of the case must be of substantially uniform hardness to prevent longitudinal stretching and head set back on firing. These properties of a case are requisite for insuring good ballistic performance of the finished cartridge and a case having such properties is hereinafter referred to as a case having satisfactory ballistic performance.

Heretofore, the combination of an accurately controlled anneal pattern such as shown at A in Fig. 1 and the cold working done by the tapering and necking dies, as indicated at H, has produced brass cartridge cases free from cracks and having satisfactory ballistic properties. However, early patterns heretofore considered indispensableto tapering operations, that is to say, the limitations which heretofore were required in an anneal pattern to insure successful tapering have been divorced from those limitations of the anneal pattern requisite for satisfactory ballisticperforman-ce. f

As a result, a wider range of anneal patterns has been made available for obtaining improved ballistic properties in steelv cartridge cases. As an example, Fig. 2 shows an anneal pattern providing an unusually short zone of anneal which is adapted to obviate longitudinal stretching by insuring uniform body hardness from head to shoulder.

It has been found that one way of successfully tapering and necking afcase and inparticular a steel case which has been quench hardened and stress relieved but not annealed; or -which has been annealed primarily for ballistic performance is to subject the upper end only ofthe case to relatively severe or abrupt work hardening such that the yield stress of the metal is localized. As a consequence, a fold attempting to propagate :Itself in the body of the case during the tapering operation will run into relatively unstressed'metal and be diffused as hereinafter described.

Referring to the drawings, Fig. 4 shows the four stages through which a .50 caliber steel case passes in being processed in accordance with the lmethod of this invention from a substantially cylindrical quench hardened and stress relieved case shown at station I tothe finished tapered and necked case shownat station 4.

The .cylindrical case shown at station l is preferably annealed to build the desired ballistic qualities into the case and it is possible that the anneal pattern may bechosen so as to reduce the pressures on thetaperi-ng dies but,.as indicated above, the discovery which characterizes the present inventionis that the tapering of the case is practically independent of the conventional taper anneal and may be successfully accomplished without such anneal by subjecting thecase to an abrupt work hardening in a limited region extending from the `mouth of the oase to a pointp on the body which, as shown in Fig. 4, is somewhat lower than the shoulders of the finished case. yThis abrupt work hardening is hereinafter Vtermed preworking and is carriedout rbyy effecting. an abrupt and relatively large reduction indiameter of a short portionw of the vupper part of the case. In the embodiment shown in the drawings, this reduction Ain diameter is substantially-0.104 inch. One method of accomplishing this abrupt reduction in diameter is to suddenly impress a relatively severe taper on the upper end of the case. The taper shown and used to constrict the.

portion w of the casecomprises an .included'angle of substantially 14 30. It` will be understood, however, that the specicanglesdescribed is the preferred angle for successfulk operation of but does not constitute alimitation on theinvention;y

and that other methods of .abruptly work hardening the metal may suggest Vthemselves as, for instance, by a sudden expansion of the metal.

The body of thecase below .thepoint p of .the preworked region 'wI has not been. taperedoriprethe metal in the region corresponding to the Ashoulder s of the finished 4case be reduced or dis- I placedso as to preclude the formation of a proper shoulder. It is well understood that the shape of theshoulder and the head to shoulder length is lcritical both from the standpoint of ballistics and successful operation in a firearm.

Thepreworking of the upper end of the case maybe accomplished by means of a suitable die stack-such as shown in Fig. 3 and which comprises a holder I0 having a top spacer block Il, a

`preworking die I2, a guide I3 and a bottom spacer block Ill. The preworking die I2 comprises a tapered annulus having the aforesaid included angle of substantially 14 30 and is adapted to be driven down over the mouth of a cylindrical case to abruptly form the relatively short steep taper w. The spacer blocks I I and I4 in conjunction with suitable adjustments of the holder I0 in the reciprocating gate of the press (not shown) constitute means for holding the preworked taper w to a predetermined region on the upper end of the oase. The metal which is abruptly preworked by the action of the tapering die I2 is strained beyond the yield point elongation of the material which reduces the tendency of the metal to fold on subsequent tapering; and being confined to the upper end of the case localizes the yield stress set up in the case during tapering, that is to say, a stress set up in the preworked portion w of the case during the body tapering operation and tending to form incipient folds in the metal will be dissipated as soon as it strikes the unstressed body portion of the case.

The body tapering operation is carried out at station 3, see Fig. 4, at which a taper correspondof the case, as shown at b in Figs, 4 and 4A.

Prior to the present invention, the body'of a case has been tapered in two operations, namely by an initial taper which partially tapers the body of the case and a final taper which completes the body taper and controls the head t0 shoulder length. In accordance with the method of this invention, the body of the case is tapered in a single operation, the body taper formed at station 3 being the final taper put on the case. This has been made possible through the discovery that by preworking a limited portion'of the -neck of the case, the yield stress is localized, andhence the propagationof taper folds in the body of the case during tapering is prevented The taper operation also pulls in the preworked-taper portion w of the case so that it is substantially straight, as shown at station 3 in Fig. 4, the shoulder point p being substantially eliminated.

Thenecking of the case and control of head to shoulder length is done at station 4, -see Fig.'4,

. at which a necking die is brought down over the much as the body has been completely tapered at the preceding station, the necking operation and head to shoulder length control are done independently of the body tapering operation.

The method of tapering and necking cartridge cases and in particular .50 caliber steel cases by preworking enables the production of finished steel cases which are free from Wrinkles or other Visual defects and Which have ballistic properties comparable to brass cases. Moreover, pre- Working has resulted in a remarkable reduction in taper scrap in the manufacture of steel cases and is applicable with equal success to brass or aluminum cases or cases of heavy geometry. And finally, preworked tapering enables steel cases to be tapered Without being annealed thereby permitting a wider range oi anneals from which to select patterns which will insure optimum ballistic perfomance,

The term bottle neck cartridge case, used for simplicity in the appended claims, identifies a cartridge case as illustrated at stage 4 in Fig. 4; such case comprising a body or powder chamber of relatively large diameter joined by a tapering shoulder to a bullet receiving neck of relatively small diameter.

What is claimed is:

1. In the forming of a bottle neck cartridge case from a substantially cylindrical tubular blank, the method which comprises the sequence of steps of: subjecting the metal which subsequently forms the neck, shoulder and immediately adjacent portion of the body, to a severe cold working; tapering the entire body by a relatively slight cold Working; and cold working the neck and shoulder to the desired iinished dimensions.

2. In the forming of a bottle neck cartridge case from a substantially cylindrical tubular blank, the method which .comprises the sequence of steps of pre-stressing the neck and shoulder 6 forming metal beyond its yield point; tapering substantially the entire body; and forming the neck and shoulder to the desired iinished dimensions.

3. In the forming of a bottle neck cartridge case from a substantially cylindrical tubular body of steel, the method which comprises the sequence of steps of hardening by cold working the metal which subsequently forms the neck, shoulder and immediately adjacent portion of the body; tapering the entire body by a relatively slight cold Working; and cold Working the neck and shoulder to the desired nished dimensions.

4. In the forming of a bottle neck cartridge case from a substantially cylindrical tubular body of steel, the method which comprises the sequence of steps of: inducing by cold Working a pattern of maximum stress in the neck forming portion, said stress diminishing through the shoulder forming portion and merging with unstressed metal in the portion of the body adjacent said shoulder; tapering the entire body by a relatively slight cold Working; and cold working the neck and shoulder to the desired finished dimensions.

JOHN P. CATLIN. GEORGE R. ECKSTEIN. MILTON B- VORDAI-IL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Callerson Dec. 31, 1918 OTHER REFERENCES Number 

